1. Field of the Invention
The present invention relates to a magnetic recording media for disk and, more particularly, to using an non-magnetic interlayer between the Cr containing underlayer and Co containing magnetic material to improve magnetic properties.
2. Description of the Prior Art
With the advent of storage media technique rapidly prompt, the most prominent features are to increase the recording density in magnetic disks.
There are several basic characteristics, such as the half amplitude pulse width (PW50), the coercivity (Hc), and the signal/noise, (S/N) ratio to assess the performance of the magnetic recording disk. Half amplitude pulse width (PW50) is ideal to be narrower so that adjacent bit interference with one another will not occur, and hence increases the packing density in a given area. A thicker magnetic film is believed to reduce the read jitter noise. Writer jitter noise, however, is known to be due to large magnetic domains having a high exchange interaction. Thus, one of approaches to reduce the noise are isolating the individual grains and/or refining the grain sizes as well as reducing the magnetic film thickness. An example of reducing the media noise is proposed by U.S. Pat. No. 5,516,547 issued to Shimizu et al.. The patent reported that admixing of SiO2 to about 10% by volume in the CoPt Cr magnetic film can reduce media noise and increase the in-plane coercivity.
In U.S. Pat. No. 5,693,426, Lee et al., proposed to control grain growth by forming an extremely thin Cr intermediate layer (20-50 xc3x85) between a Co-based magnetic alloy and an underlayer having B-2 structure. The characteristic of recording media structure Lee proposed includes that a Cr intermediate layer and Co-based magnetic film are formed sequentially and epitaxially on the B-2 structure. Lee observed it has properties of increase in coercivity and hysteresis loop squarensess.
Ohkijima et al., on the paper of IEEE, 5, p2944 (1997), titled xe2x80x9cEffect of CoCr Interlayer on Longitudinal Recordingxe2x80x9d further proposed a CoCr interlayer structure for the recording media. They found that the media structure with a CoCr 37 interlayer between Co-alloy magnetic layer and the Cr underlayer has better performances in coercivities and S/N of media than without interlayer. Ohkijima et al., also investigated the structure of the media with and without a CoCr interlayer by using TEM cross-sectional view. Ohkijima found that the grain growth at the boundary between the Cr underlayer and CoCrTa magnetic layer is discrete. By contrast, the grain grows continuously between the boundary of CoCr interlayer and the CoCrTa magnetic layer. Thus Ohkijima concluded that the CoCr interlayer could improve the lattice matching at the boundary of the CoCrTa layer.
A magnetic recording medium using a nonmagnetic interlayer in between a Cr-base underlayer and a Co magnetic layer is disclosed. The nonmagnetic interlayer comprises Co1xe2x88x92xcex1xe2x88x92xcex2xe2x88x92xcex3xe2x88x92xcex6Crxcex1Xxcex2Yxcex3Zxcex6. X is a material selected from Ni or Fe so as to substitute a portion of Cr composition. Y is a material selected from materials which can form a solid solution with at least one of list materials consisting of Ni, Fe, Co, and Cr. The Y material added in the interlayer is to adjust the lattice mismatch between the interlayer and the under layer to a magnitude so that the interlayer formed on the underlayer at least have a preferred orientation, an epitaxial layer is best preferred. The Y material can be chosen from elements such as V, Mo, Ru, Ti, and Mn. However, Z is a material which is insoluble with any of above list materials, Cr, Co, X, and Y in a solid state so as to form precipitates, thereby inhibiting the grain growth. The Z material can be selected one among B, Ta, Nb, Zr, W, oxides and nitrides. In a preferred embodiment, the xcex1, xcex2, xcex3, and xcex6 are at a range of about 25-41%, 0.1-5%, 0.1-5%, and 0.1-5%, respectively. The interlayer thickness is of between about 0.5-20 nm.